In conventional ultrasound imaging, ultrasonic signals having a frequency of 1-15 MHz are transmitted from a transducer and into a region of interest. Return echo signals are detected by the transducer, converted to a digital format and analyzed with a microprocessor (CPU) or digital signal processor (DSP) to produce information about tissue structure or fluid movement in the region of interest. At these frequencies and with a frame rate of 30-60 Hz, it is not too difficult to transmit the ultrasound data from the transducer to a console or other computing system. However, as the pulse repetition frequency (PRF) of the ultrasound signals transmitted by the elements increases, the amount of ultrasound echo data that must be transmitted from the transducer to the processor increases dramatically.
One emerging field in ultrasound that is particularly affected by this data bottle neck is plane wave imaging. In most modern ultrasound imaging systems, ultrasound signals that are transmitted from, and received by, multiple transducer elements are delayed, weighted and summed to direct the transmit and receive beams in a particular direction. The time required to scan a region of interest is therefore the time required to produce and receive anywhere from several to a few hundred beam lines that cover the area. With plane wave imaging, ultrasound signals are simultaneously transmitted by each transducer element and the corresponding electronic echo signals produced by each transducer element are sampled without combining them with the signals produced by the other elements. The time required to scan a region of interest is therefore only limited by the time it takes an ultrasound signal to penetrate to a desired depth in the tissue and return to the transducer. With plane wave imaging, frame rates of 3,000-15,000 Hz are possible compared with frame rates of 30-60 Hz with conventional imaging techniques. The frame rates achievable with plane wave imaging are useful for such tasks as imaging quickly moving tissues (e.g. heart muscles of small animals) as well as for studying the effects of shear waves in tissue among other uses.
With such high PRFs, the amount of ultrasound data that must be transmitted from the transducer to one or more processors that analyze the data can exceed tens of Gigabits per second. Therefore, one limiting factor in real time, plane wave imaging is how fast the data can be transmitted from the transducer to the signal processing system that analyzes the data. Given this problem, there is a need for techniques to reduce the amount of data that is transmitted from an ultrasound transducer and/or to shorten the time required to transmit the data to the processors that analyze the data.